(1) Field of Invention
The present invention relates to a Spectrometer and more particularly to an electro-optic imaging Fourier transform spectrometer comprising a single optical path in which the intensity of light that exits the spectrometer after the light traverses an input polarizer, a series of adjustable birefringent phase retarders, and an output polarizer is simply related by the total optical phase delay to a portion of the frequency spectrum of the light.
(2) Description of Related Art
Fourier transform spectrometers (FTS) have long been known in the art. FTSs require large changes in total optical path length traversed by a beam of electromagnetic radiation. This has typically been accomplished by scanning Michelson interferometers in which one mirror of the interferometer is physically moved to change its length. Such an interferometer design has the advantage that a large, continuous band of frequencies can be resolved by scanning large distances with the great precision usually enjoyed by modern mechanical devices. However, because of the necessity to move large distances, such interferometers tend to be very large, heavy, slow, have many moving parts, require ultra-precise alignment, and consume relatively large amounts of power to operate.
The motivation for the present invention was partially born from a need to take a FTS into orbit around Earth and every problem mentioned in the above paragraph becomes exacerbated in the context of space missions: being large and heavy significantly increases the cost of launching the FTS into orbit; as the satellites typically orbit through the atmosphere at speeds upwards of 17,000 miles per hour, they can pass through relevant samples very quickly, requiring faster-than-normal operational scanning speeds; many moving parts makes mechanical failure more likely during the violent launch period; once launched, the satellites must function on their own without human intervention, making any alignment tolerances problematic as they cannot ever be realigned; and lastly, large power consumption means that, for a given mission lifetime, either more fuel must be taken along with the satellite or larger solar panels must be used in orbit, both of which drastically increase the cost of a space mission.
In addition to the shortcomings of modern FTSs with regard to space missions, the same shortcomings of commercial FTSs and wave-meters, namely that they are expensive, large, and slow, are notable in the modern-day research laboratory.
Thus, a continuing need exists for an improved FTS that is more compact, lighter-weight, faster, has fewer moving parts, is less sensitive to alignment, and consumes less power than the FTSs that are currently available.